March 26, 2008
Jet Propulsion Laboratory, Pasadena, Calif.
CASSINI TASTES ORGANIC MATERIAL AT SATURN’S GEYSER MOON
PASADENA, Calif. – NASA’s Cassini spacecraft tasted and sampled a
surprising organic brew erupting in geyser-like fashion from Saturn’s
moon Enceladus during a close flyby on March 12. Scientists are
amazed that this tiny moon is so active, “hot” and brimming with
water vapor and organic chemicals.
New heat maps of the surface show higher temperatures than previously
known in the south polar region, with hot tracks running the length
of giant fissures. Additionally, scientists say the organics “taste
and smell” like some of those found in a comet. The jets themselves
harmlessly peppered Cassini, exerting measurable torque on the
spacecraft, and providing an indirect measure of the plume density.
“A completely unexpected surprise is that the chemistry of Enceladus,
what’s coming out from inside, resembles that of a comet,” said
Hunter Waite, principal investigator for the Cassini Ion and Neutral
Mass Spectrometer at the Southwest Research Institute in San Antonio.
“To have primordial material coming out from inside a Saturn moon
raises many questions on the formation of the Saturn system.”
“Enceladus is by no means a comet. Comets have tails and orbit the
sun, and Enceladus’ activity is powered by internal heat while comet
activity is powered by sunlight. Enceladus’ brew is like carbonated
water with an essence of natural gas,” said Waite.
The Ion and Neutral Mass Spectrometer saw a much higher density of
volatile gases, water vapor, carbon dioxide and carbon monoxide, as
well as organic materials, some 20 times denser than expected. This
dramatic increase in density was evident as the spacecraft flew over
the area of the plumes.
New high-resolution heat maps of the south pole by Cassini’s Composite
Infrared Spectrometer show that the so-called tiger stripes, giant
fissures that are the source of the geysers, are warm along almost
their entire lengths, and reveal other warm fissures nearby. These
more precise new measurements reveal temperatures of at least minus
135 degrees Fahrenheit. That is 63 degrees Fahrenheit warmer than
previously seen and 200 degrees Fahrenheit warmer than other regions
of the moon. The warmest regions along the tiger stripes correspond
to two of the jet locations seen in Cassini images.
“These spectacular new data will really help us understand what powers
the geysers. The surprisingly high temperatures make it more likely
that there’s liquid water not far below the surface,” said John
Spencer, Cassini scientist on the Composite Infrared Spectrometer
team at the Southwest Research Institute in Boulder, Colo.
Previous ultraviolet observations showed four jet sources, matching
the locations of the plumes seen in previous images. This indicates
that gas in the plume blasts off the surface into space, blending to
form the larger plume.
Images from previous observations show individual jets and mark places
from which they emanate. New images show how hot spot fractures are
related to other surface features. In future imaging observations,
scientists hope to see individual plume sources and investigate
differences among fractures.
“Enceladus has got warmth, water and organic chemicals, some of the
essential building blocks needed for life,” said Dennis Matson,
Cassini project scientist at NASA’s Jet Propulsion Laboratory in
Pasadena, Calif. “We have quite a recipe for life on our hands, but
we have yet to find the final ingredient, liquid water, but Enceladus
is only whetting our appetites for more.”
At closest approach, Cassini was only 30 miles from Enceladus. When it
flew through the plumes it was 120 miles from the moon’s surface.
Cassini’s next flyby of Enceladus is in August.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The mission is
managed by JPL for NASA’s Science Mission Directorate, Washington.
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